DANSK DS/EN IEC 61158-4-25 PDF

The data-link layer provides basic time-critical messaging communications between devices in 137 an automation environment. 138 This protocol provides communication opportunities to all participating data-link entities, 139 sequentially and in a cyclic synchronous manner. Foreground scheduled access is available 140 for time-critical activities together with background unscheduled access for less critical 141 activities. 142 Deterministic and synchronized transfers can be provided at cyclic intervals up to 1 ms and 143 device separations of 25 km. This performance is adjustable dynamically and on-line by re144 configuring the parameters of the local link whilst normal operation continues. By similar 145 means, DL connections and new devices may be added or removed during normal operation. 146 This protocol provides means to maintain clock synchronization across an extended link with 147 a precision better than 10 μs. 148 This protocol optimizes each access opportunity by concatenating multiple DLSDUs and 149 associated DLPCI into a single DLPDU, thereby improving data transfer efficiency for data150 link entities that actively source multiple streams of data. 151 The maximum system size is an unlimited number of links of 99 nodes, each with 255 DLSAP152 addresses. Each link has a maximum of 224 related peer and publisher DLCEPs.